Pulper



April 14, 1970 I E. H. CUMPSTON, JR 3,

v PULPER Filed March 31, 1967 s Sheets-Sheet 1 FIG. I

INVENTOR. EDWARD H. CUMPSTON, JR.

HIS ATTORNEYS.

April 14, 1970 E. H. CUMPSTON, JR 3,506,202

PULPER 3 Sheets-Sheet 2 Filed March 31, 1967 I l m' INVENTOR.

EDWARD H. CUMPSTON, JR.

BY Mm MKW FIG.

HIS ATTORNEYS.

April 14, 1970 E. H. CUMPSTON, JR

PULPER 3 Sheets-Sheet 5 Filed March 31, 1967 INVENTOR. I EDWARD H.CUMPSTON, JR.

FIG,

HIS ATTORNEYS.

United States Patent Ofifice 3,506,202 Patented Apr. 14, 1970 US. Cl.241 97 26 Claims ABSTRACT OF THE DISCLOSURE An improved pulper uses arelatively large refiner or defibering unit with ridged confrontingfaces on its stator and rotor, and the inlet openings to the refiningpassageway are arranged around the center of the rotor and protected bya shield to admit only clean pulp to the refiner. An outlet opening forrefined pulp is arranged around the periphery of the stator. Thedefibering unit is at least one half the tank diameter to provide alarge refining area and considerable pumping force on the pulp material.Vanes mounted on top of the rotor break up and swirl the pulp materialto create a centrifugal force augmenting the pumping force of therefiner to drive pulp radially outward away from the refiner and thusspeed up circulation through the refiner. Tank Walls are smooth andunbaffied to facilitate such swirling, and deflector vanes are mountedon the tank wall just below the working surface to limit the height ofthe swirl and to turn over the pulp material at its peripheral surfaceto speed up recirculation of material through the refiner.

The invention comprises improved apparatus for pulping processes inwhich dry paper making material is reduced to individual fibers in awater suspension. Pulping as known in the prior art is accomplished in atank filled with water and into which dry paper making material isintroduced. One or more refining or defibering units are driven byelectric motors to mechanically reduce the pulp material to individualfibers in either a batch or continuous process. The process is used onboth fresh fibrous material and broke or fibrous waste material that isrepulped. The latter often includes foreign objects such as bits ofmetal, glass, or other materials that cannot be defibered. Such foreignmaterials must be cleaned out of the pulper, and can damage or clog therefiner if they enter it. Hence, it is important to keep foreignmaterials out of the refiner, and it is easier to separate suchmaterials from the pulp material if they have not been broken into smallbits by passing through the refiner. Prior art equipment has sufferedserious shortcomings in not successfully keeping foreign materials outof the refiner, and in general inefficiency and unreliability.

The objects of the invention include, without limitation, the following:

(a) Overcoming the deficiencies of prior art pulping equipment;

(b) Keeping foreign material out of a pulping refiner;

(c) Improved efliciency and reliability in a pulper;

(d) A pulping refiner that is rugged and simple, easily adjustable,reliable, and long-lived;

(e) Reducing the power consumption and improving the performance of apulper;

(f) Providing continuous adjustment between the working surfaces of apulp refiners rotor and stator to keep the shearing forces adjusted toan optimum;

(g) Speeding up the circulation of pulp material in a pulper for fasterdefibering and greater efiiciency;

(h) Facilitating the removal of contaminants and foreign objects frompulping equipment; and

(i) Allowing continuous removal of defibered material from a pulperwithout removing under-refined material or over-working suificientlydefibered material.

These and other objects of the invention will be apparent hereinafterfrom the specification which describes the invention, its use,operation, and preferred embodiments, from the drawings, whichconstitute a part of the disclosure, and from the subject matterclaimed.

Generally, improved defibering efiiciency for a pulper is accomplishedaccording to the invention with a relatively large refiner formed eitheras a single rotor or a combined rotor and stator having large, fiat,annular surfaces each provided with many ridges that confront to form arefining passageway. Preferably, the refiner is arranged at the centerof the bottom of a generally cylindrical tank and is about /2 thediameter of the tank. Such a relatively large refiner exertsconsiderable pumping force to drive material radially outward from therefiner and draw material into the refiner for rapid circulation. Thisis augmented by vanes on top of the rotor that break up and swirl thepulp to drive it radially outward by centrifugal force. The lower halfof the tank is smooth-walled and unbaffled to facilitate such swirling,and deflector vanes are arranged around the tank wall just below theworking surface to limit swirl height and to turn over surface pulp tospeed its reentry into the refiner region. The refiner can also be usedin other locations such as a tank wall or in a pipeline. Apertures nearthe center of the rotor disk admit fibrous material to the radiallyinward edge of the refining passageway, the ridges subject it to severemechanical shear for breaking the material into individual fibers.

Improved ability to keep foreign material and debris out of the refineris generally accomplished by two improvements. First, the inlet to therefining passageway is formed by apertures near the center of the rotordisk. The moving apertures in their radially inward position admitfibers of light mass to the refining passageway, but larger masses anddenser foreign materials are urged outward by the pumping effect of therotor and do not ordinarily enter the rotating inlet apertures. Second,the inlet apertures are preferably covered by an adjustable shieldarranged so that material must turn over the periphery of the shield andtravel radially inward to be drawn into the inlet apertures. Foreignmaterial and debris of generally greater density and larger size isdriven outward by the centrifugal flow of pulp at the periphery of theshield, and cannot turn radially inward to enter the inlet apertures ascan the relatively lighter fibrous material.

For continuous pulping, an outlet for defibered pulp is preferablyarranged near the periphery of the stator to insure that only properlyrefined material of relatively small size is withdrawn against thecentrifugal flow which tends to carry larger, incompletely refinedmaterial out into the tank for recirculation through the refiner.

In the drawings:

FIG. 1 is a partially sectioned, partially elevational, and partiallycut-away, side view of a pulper according to the invention;

FIG. 2 is a plan view of a refining surface for the rotor of the pulperof FIG. 1;

FIG. 3 is a plan view of the refining surface of the stator of thepulper of FIG. 1;

FIG. 4 is an enlarged fragmentary elevation of the rotor of FIG. 2;

FIG. 5 shows a partially cut-away side elevation of the pulper of FIG.1;

FIG. 6 shows a partially cut-away plan view of the pulper of FIG. 1; and

FIG. 7 shows an enlarged, fragmentary elevation of an alternative rotorand stator ridge configuration.

Throughout the drawings, corresponding parts are identified by the samereference numerals. Although the inventive pulper improvement can beused in a variety of pulping equipment, the invention will be describedrelative to the illustrated preferred embodiment.

Referring particularly to FIG. 1, the inventive pulper comprisesdefibering or refining unit 20 preferably mounted in the center of thebottom of pulping tank which is partially cut-away for convenience ofillustration. Defibering unit generally comprises stator 12 mounted onthe bottom of tank 10, and rotor 11 mounted on drive shaft 13 driven bya conventional sheave 14 with belts and a motor (not shown). Packinggland 15 seals the opening in the bottom of tank 10 for shaft 13, andshaft 13 is mounted in bearings in a known way in quill 16 which ismovable axially in frame 17. Arm 18 mounted for pivotal motion on pin 19is connected to bracket 21 on quill 16 for sliding quill 16 axially inframe 17 to position rotor 11 axially relative to stator 12. Arm 18 ispositioned vertically by screw 23 extending through nut 22 at the outerend of arm 18, and adjusted by hand wheel 24. Of course, power adjustingmeans such as an hydraulic cylinder or an electric gear motor can beused for positioning quill 16. By such adjusting means rotor 11 can bepositioned axially to adjust its clearance from stator 12 even duringoperation of the pulper.

Stator 12 is formed generally of a base plate 25 secured to the bottomof tank 10, and refining plates 26 screwed to the upper surface of baseplate 25 (as best shown in FIGS. 1 and 3). Refining plates 26- arepreferably formed as identical sectors of an annular area around theperiphery of base plate 25 rather than forming the entire statorrefining surface of one large integral piece. The advantages includemore economical manufacture, especially of a large stator, and easyreplacement of worn or defective plates 26. Plates 26 are preferablyformed of a hard material such as hardened steel, and are provided withridges 27 separated by grooves 28. Ridges 27 extend generally radiallyof stator 12 as illustrated in FIG. 3, and are formed with generallyparallel and upright sides and flat top portions similar to rotor ridgesillustrated in FIG. 4 and described below. A preferred alternative formof refining ridges having sloping side walls are illustrated in FIG. 7and described below. With either configuration, ridges 27 provide amultitude of abrupt surfaces for mechanically shearing and defiberingpulp in the refining passageway between stator 12 and rotor 11.

Outlet or extraction holes 29 are formed around the periphery of stator12 to extract refined pulp from tank 10. An extraction channel orconduit 30 is arranged beneath outlet openings 29, and conduit 30connects with an outlet pipe 31 which is normally connected to a pump(not shown). Extraction of refined pulp through outlet openings 29 nearthe periphery of stator 12 at a point in the refining passage-way atwhich pulp is subjected to generally centrifugal outward flow, insuresthat only refined and relatively small fibers are drawn down throughoutlet openings 29 against the centrifugal flow tending to force anyheavier and incompletely refined particles out to the periphery ofstator 12. Gutlet conduit 30 can also be arranged to open into thebottom of tank 10 around the periphery of stator 12 to, the same generaleffect. This also avoids holes 29 in stator 12 and increases the workingarea of stator 12.

As best shown in FIGS. 1, 2, and 4, rotor 11 is formed of a generallyclosed disk or plate 32 secured to drive shaft 13 with several refiningsurface sector plates 33 screwed to the underside of disk 32. Sectorplates 33 are each formed with a plurality of generally radial ridges 34and grooves 35, and are preferably formed of a hard, corrosion-resistantmaterial. As best illustrated in FIG. 4, each ridge 34 is formed withgenerally vertical side walls 36 communicating with a top wall 37, andeach of the ridges 34 is connected by a grooved bottom 38.

An alternative preferred embodiment of ridges for rotor 11 isillustrated in FIG. 7. Ridges 47 on sector plate 3311 have generallyflat tops 48 and sloping side walls 49 which tend to prevent the groovesbetween ridges 47 from clogging with pulp material. Correspondingsloping sided ridges are preferred for stator 12 so that the refiningsurfaces of both the rotor and stator are made self cleaning. The angleA between confronting sloping surfaces 49 can be any of a variety ofangles preferably from between 60 to 120. In one preferred embodiment ofthe invention angle A is formed at 60 as illustrated for the rotor andat for the stator ridges, but many different angles are possible withinthe spirit of the invention. The sides and edges of such ridges providesa multitude of shearing surfaces for defibering pulp as rotor 11 isdriven relative to stator 12.

As best shown in FIGS. 1, 5, and 6, rotor 11 has a plurality of vanes 41arranged around its upper periphery. As rotor 11 is driven in theindicated direction, vanes 41 drive pulp material outward in a pumpingaction from the periphery of rotor 11 and circulate pulp materialthrough tank 10 in a swirling motion as indicated by arrows. Vanes 41also serve to break up pulp material into flake size for the refiner 20,and vanes 41 on rotor 11 can successfully accomplish pulping Withoutstator 12 or any refining passage-way.

Although refiner 20 is illustrated as arranged on the bottom of tank 10,it is possible to use the inventive refiner in other environments. Forexample, refiner 20 could be positioned in an enlarged space in a pipeline, or could be located on the vertical wall of a tank. Incircumstances in which it is not essential for refiner 20 to impart aswirling motion to material to be pulped, and in which such material isfed to refiner 20 in flake size suitable for defibering, vanes 41 can beomitted.

Inlet openings 40 are formed through disk 32 and sector plates 33 toadmit material from tank 10 to the radially inward edge of the refiningpassageway formed by ridges on rotor 11 and stator 12. Pulp materialdrawn into the refining passageway through openings 40 is pumpedradially outward between rotor 11 and stator 12.

Inlet openings 40 in rotor 11 are preferably covered by shield 42mounted at the center of disk 32. Shield 42 is spaced above disk 32 toallow material from tank 10 to pass around the periphery of shield 42into openings 40. To force material to turn radially inward around theperiphery of shield 42 in entering into openings 40, shield 42preferably extends at least to the centers of openings 40 which arepreferably equidistant from the axis of rotor 11. The diameter of shield42 and its clearance from disk 32 are related in creating conditionskeeping overly large or foreign materials from turning radially inwardinto rotor openings 40.

Shield 42 is convex as shown in FIG. 1 with its center extending up intotank 10 slightly more than its periphery to guide the flow of pulpmaterial downward and outward at the upper surface of rotor 11. However,a flat topped shield works quite satisfactorily and is less expensivethan convex shield 42. Also shield 42 is preferably axially adjustablerelative to disk 32 to adjust the clearance between disk 32 and shield42 over inlet openings 40. Such axial adjustment can be accomplished byshims or other known means, or by replacing shield 42 with anothershield having greater or less clearance over disk 32 as desired.

The preferred relative size and positions of tank 10 and refiner 20 arebest shown in FIGS. 5 and 6. Tank 10 is preferably an upright, rightcircular cylinder, and refiner 20 is preferably mounted in the center ofthe bottom of tank 10. The bottom of tank 10 is preferably flat asillustrated or slightly sloping or concave to allow draining of tank'10. The working levels of pulp material in tank 10 range from thenormal level indicated by dashed line 43, to a low level indicated bydashed line 44. The inside of tank 10 is preferably smooth-walled, andat least the lower half of tank 10 is unbafiled as shown in FIG. 5.

The relatively large size of refiner 20 not only provides a largerefining area for pulp material, but exerts a substantial pumping forcedriving material radially outward. The unobstructed bottom of tank 10allows the pulp to move rapidly away from refiner 20 toward the verticalwalls of tank so that refiner 20 can draw in pulp material at a highrate of circulation. At the same time, the unbafiled lower half of tank10 allows free swirling of material to create a centrifugal forceaugmenting the pumping action of refiner 20.

The pumping and centrifugal force from refiner 20 not only draws pulpmaterial rapidly through refiner 20 and drives pulp radially outwardfrom refiner 20, but such forces make the pulp material swirl and risearound the periphery of tank 10, return toward the center of tank 10across the upper surface of the liquid, and be drawn downward throughthe center of tank 10 to refiner 20 in a rapid circulation. Such freeswirling of pulp material in a tank is contrary to the usual procedureof bafliing the tank to restrict swirling motion and increase the speedof the rotor relative to the pulp material.

A plurality of small, streamlined deflector vanes 45 are arranged on theinside wall of tank 10 just below the intended working surface. Vanes 45are preferably set approximately 45 to the vertical and are oriented tothe normal swirling motion of pulp material to give an uplift to suchmaterial at its peripheral working surface to hasten the turnover andreturn of pulp material to the central portion of the tank and down tothe region of refiner 20. Vanes 45 are preferably streamlined asillustrated in FIGS. 5 and 6 for minimum obstructing of normal swirlingmotion of the slurry in tank 10, and as best shown in FIG. 5, vanes 45are positioned at different elevations to insure that some vanes arepositioned just below either normal working surface 43 or low workingsurface 44. The uplift and turnover force imparted to the swirlingslurry by deflector vanes 45, speeds up the circulation of pulp materialthrough refiner 20 and prevents pulp from swirling in stratified bundlesof fibers tending to collect at the periphery of the tank. Vanes 45 tendto lift and turn over such bundles of fibers to force them toward thecenter of the tank for submerging toward refiner 20. Vanes 45 are notnumerous enough or large enough to substantially baffle the swirlingmotion of pulp material in tank 10, but vanes 45 are arranged insufficient numbers and sizes to limit the height of swirling pulpmaterial next to the walls of tank 10.

The inventive refiner and tank arrangement has been found to increasethe rate of pulping over conventional tanks and pulping equipment byfrom 25% to 50% with no increase in power. At the same time the solidmaterial in the liquid can be increased from the prior art level ofabout 3% to about 6% in the inventive pulper. This eifects a substantialeconomy in addition to the improved efficiency of refiner 20 overpreviously known pulp defibering units.

Refiner 20 is preferably at least /2 the diameter of tank 10 to takeadvantage of the power economy of moving a large volume of slurry at alow velocity rather than moving a small volume at high velocity.Circulation of slurry follows the conservation of momentum law, holdingcirculation C equal to velocity V times mass moved M or C: VM. The powerP required to move a mass M of slurry follows the conservation of energylaw and is equal to /2MV (P= /zMV Increasing the diameter of refiner 20not only greatly reduces the power required to circulate slurry in thetank, but increases the working area of the refining passageway ofrefiner 20 by a power of 2. For example doubling the diameter of arelatively small refiner increases its working area A by 4 times. I

The mass moved by a refiner is equal to its working area A times itsvelocity V. (M=A V.) This proportion exists because mass is related tothe discharge circumference of the refiner and the thickness of themoving layer in the refining passageway, both of which increase as disksize increases. For example, if the diameter of a relatively smallrefiner (M =A V, and C =VM is doubled and its velocity is halved, thenew mass M of moved slurry will be M =4AX /2V=2M and the new circulationwill be C =M /2.V=2M X' /2V=M V, or the same as with the smaller diskdiameter. However, the power for the larger refiner [P /2M /2V) will beP /2 2M /2V) AM V which is only /2 the /zM V required by the smallerdisk to produce the same rate of circulation. This example demonstratesthe importance of a relatively large diameter for refiner 20. Of course,an optimum diameter for refiner 20 is limited by the diameter of tank10, the manufacturing costs of a larger refiner, and fluid flowconsiderations between the circumference of the refiner and the verticaltank wall. From experience, I have found that an optimum refinerdiameter is /2 the tank diameter or slightly larger.

In operation, tank 10 is filled with water, and fibrous material to bepulped is furnished into the tank. Rotor 12 is driven to rapidlycirculate the pulp material into contact with vanes 41 which easily tearthe material into small flakes. As the size of these flakes diminish,they become more and more resistant to defibering shear from vanes '41,but the pumping action between rotor 11 and stator 12 draws sufficientlysmall and light flakes over the periphery of shield 42 and radiallyinward into inlet openings 40 to enter the refining passageway betweenrotor 11 and stator 12. The ridges on the refining surfaces of the rotorand stator subject the flakes to severe hydraulic and mechanicalshearing action to defiber them. Defibered material is either drawncontinuously into outlet conduit 30 and outlet pipe 31, or the pulpercan be operated on a batch basis with delivery of defibered materialfrom the periphery of refiner 20 back into tank 10.

Shield 42 prevents foreign material, debris, or oversized material fromentering inlet openings 40, since larger objects of greater mass aremore subject to the centrifugally outward pumping force of refiner 20,and cannot turn radially inward under shield 42 before they are sweptradially outward by the main flow of slurry over vanes 41. As a furthercleaning effect, shield 42 is positioned relatively closely over the topof the rotor to guard inlet openings 40 from foreign matter andcontaminants by size as well as by mass. Objects larger than theclearance of shield 42 over disk 32 cannot enter openings 40 even ifthey were light enough to turn radially inward against the centrifugalforces at the periphery shield 42. Such cleaning action of shield 42 androtating inlet openings 40 in rotor 11 prevents damage to the refiningsurfaces of the rotor and stator from any foreign matter.

Foreign matter and contaminants are removed from tank 10 by knownmethods of settling into a trap or being caught by trailing wire.Foreign matter that has not been broken down by passage through refiner20 is easier to remove from the inventive pulper than broken or finelydivided contaminants which are difficult to separate from the usuablefibers.

It will thus be seen that the inventive pulper accomplishes the objectsset out above. Other features, advantages, and other specificembodiments of this invention will be apparent to those exercisingordinary skill in the pertinent art after considering the foregoingdisclosure. In this regard, while a specific preferred embodiment hasbeen described in detail, such disclosure is intended as illustrative,rather than limiting, and other embodiments, variations, andmodifications can be effected within the scope and spirit of theinvention as disclosed and claimed. Furthermore, the following claimedsubject matter is intended to cover fully all the aspects of thedisclosed invention that are unobvious over prior art, including allequivalent embodiments.

I claim:

1. An improved pulping machine comprising:

(a) a tank having a generally cylindrical vertical wall and anunobstructed bottom, at least the bottom half of said tank beingsubstantially smooth-walled and unbaflfled and said tank being arrangedfor containin g material to be pulped;

(b) a refiner arranged on said bottom and including a fiat rotoroverlying a refining passageway and disposed for substantial, radialpumping through said passageway;

(c) a plurality of vanes arranged on the upper periphery of said rotorto impart swirling motion to said material in said tank; and

(d) said refiner being at least one half the diameter of said tank.

2. The pulping machine of claim 1 including a plurality of streamlineddeflector vanes arranged on said vertical wall in the upper half of saidtank below and near the working surface for said tank, said deflectorvanes being oriented generally in the direction of said swirling motionand tilted to turn over said material at the periphery of said workingsurface to hasten the reentry of said material into the region of saidrefiner.

3. The pulping machine of claim 1 wherein said diameter of said tank isapproximately 1.5 times the distance from said bottom to said workingsurface for said tank.

4. The pulping machine of claim 1 wherein said refiner is concentricwith said bottom and said bottom is substantially fiat.

5. The pulping machine of claim 1 wherein said refiner comprises:

(a) a stator comprising a generally planar, annular, refining surfacefacing into said tank and formed with a plurality of generally radialridges;

(b) a rotor comprising a generally closed disk overlying and extendingto the periphery of said stator, the face of said disk confronting saidstator, having a generally planar, annular refining surface formed witha plurality of generally radial ridges extending into proximity withsaid stator refining surface to form said refining passageway betweensaid stator and said rotor;

(c) said plurality of vanes being arranged on said rotor disk around theperiphery of said rotor disk on the tank side of said rotor disk; and

(d) said rotor disk being formed with a plurality of apertures throughsaid disk and disposed radially inward of said vanes adjacent a radiallyinward portion of said refining passageway to admit material from saidtank through said apertures to said inward portion of said passagewayfor a refining pass radially outward through said passageway toward theperiphery of said stator and rotor.

6. The pulping machine of claim 5 including means for axially adjustingsaid rotor disk relative to said stator for varying the spacing betweensaid rotor disk and said stator.

7. The pulping machine of claim 6 wherein said refiner is concentricwith said bottom and said bottom is substantially flat.

8. The pulping machine of claim 6 wherein said adjusting means comprisesan axially movable drive shaft for said rotor disk, a quill supportingsaid drive shaft, a pivoted lever for moving said quill axially toposition said drive shaft and said rotor disk, and means for adjustingsaid lever.

9. The pulping machine of claim 5 wherein a liquid tight shield isarranged in spaced relation to said rotor disk over the central portionof said rotor disk on the tank side thereof, and said shield extendsradially outward at least to the center of said apertures in said rotordisk.

The pulping machine of claim 9 wherein said apertures in said rotor diskare equidistant from the axis of said disk.

11. The pulping machine of claim 5 wherein an outlet opening is formedin the region of the periphery of said stator and including conduitmeans communicating with said outlet opening for extracting refinedmaterial from said tank through said outlet opening.

12. The pulping machine of claim 11 including a plurality of streamlineddeflector vanes arranged on said vertical wall in the upper half of saidtank below and near the working surface for said tank, said deflectorvanes being oriented generally in the direction of said swirling motionand tilted to turn over said material at the periphery of said workingsurface to hasten the reentry of said material into the region of saidrefiner.

13. The pulping machine of claim 5 wherein said diameter of said tank isapproximately 1.5 times the distance from said bottom to said workingsurface for said tank.

14. In a pulping machine having a stator, a rotor, and means for drivingsaid rotor in rotary motion relative to said stator, the improvementcomprising:

(a) said stator comprising a generally planar, annular, refining surfaceformed with a plurality of generally radial ridges;

(b) said rotor comprising a generally closed disk overlying andextending to the periphery of said stator, the face of said diskconfronting said stator having a generally planar, annular refiningsurface formed with a plurality of generally radial ridges extendinginto proximity with said stator refining surface to form a refiningpassageway between said stator and said rotor; and

(c) said rotor disk being formed with a plurality of apertures throughsaid disk spaced substantially inward from the periphery of said diskand disposed adjacent a radially inward portion of said refiningpassageway to admit material to said inward portion of said passageway,for a refining pass radially outward through said passageway toward theperiphery of said stator and rotor.

15. The pulping machine of claim 14 including means for axiallyadjusting said rotor disk relative to said stator for varying thespacing between said rotor disk and said stator.

16. The pulping machine of claim 15 wherein said adjusting meanscomprises an axially movable drive shaft for said rotor disk, a quillsupporting said drive shaft, a pivoted lever for moving said quillaxially to position said drive shaft and said rotor disk, and means foradjusting said lever.

17. The pulping machine of claim 14 wherein a liquid tight shield isarranged in spaced relation to said rotor disk over the central portionof said rotor disk on the tank side thereof, and said shield extendsradially outrlvaid at least to the center of said apertures in saidrotor 18. The pulping machine of claim 17 wherein said apertures in saidrotor disk are equidistant from the axis of said disk.

19. The pulping machine of claim 17 wherein the central portion of saidshield extends into said tank at least as far as the peripheral portionof said shield, and said peripheral portion of said shield is spacedfrom said rotor by at least .25 inch.

20. The pulping machine of claim 14 wherein an outlet opening is formedin the region of the periphery of said stator and including conduitmeans communicating with said outlet opening.

21. The pulping machine of claim 14 wherein said ridges on said refiningsurfaces of said rotor and said stator each comprise generally slopingside surfaces communicating with a flat top surface.

22. The pulping machine of claim 14 wherein said stator and said rotordisk are disposed in a tank and a plurality of vanes are arranged onsaid rotor disk around the periphery of said rotor disk on the tank sideof said rotor disk.

23. The pulping machine of claim 22 wherein said tank has a generallycylindrical vertical wall and a substantially flat bottom and saidstator and said rotor disk are concentric with said tank bottom.

24. The pulping machine of claim 14 including a tank 9 and wherein saidrotor is arranged over the bottom of said tank and is at least thediameter of said tank.

25. The pulping machine of claim 1 wherein said rotor is arranged overthe bottom of said tank and is up to 1 inch thick.

26. The pulping machine of claim 25 wherein said rotor is spaced atleast 3 inches above said bottom of said tank.

References Cited Jones 241260 X =Dalze1l 241-260 X Vokes 241-46.11

Jones 241152 X Sargood 241260 Morton 24146.11

ROBERT C. RIORDON, Primary Examiner D. G. KELLY, Assistant Examiner US.Cl. X.R.

